I've been undereating lately... but more because there's no fucking food. I eat breakfast at 6am and then nothing more until dinner, at 6-8pm. I want more vegetables, damnit! Then again, I've been making myself eat less anyway.
I know what it's like to snack a lot, whenever my parents go on vacation without me I end up eating 3x as much as I usually do out of loneliness, if not more. It's horrible. But unless you're REALLY stubborn, I think it'd be better to just discipline yourself.